As is disclosed in copending application of Norman F. Costello et al. Ser. No. 286,568 filed July 24, 1981, now U.S. Pat. No. 4,401,091, one form of heat transfer device, shown embodied in an oil temperature regulator, includes a flow passage for one of the fluids defined by spaced surfaces of first and second boundary members and specifically of substantially concentric tubes. The intervening space is bounded by generally radiating fins of a soft metal such as copper, brass or the like that are very thin and usually provided with louvers so as to cause turbulence and efficient heat transfer between one of these boundary members or tubes and the fluid flowing through the space and the fins.
The fin that spans the fluid space is conveniently a serpentine fin strip having opposite crests adjacent the spaced surfaces. This serves as a heat transfer fin and as a turbulator as mentioned above. In many embodiments, the inner boundary member or tube is made of molded plastic. In addition, the fin height of the strip or the spacing between the sets of opposite crests varies from the intended dimensions and results frequently in a loose fit of the fin within the space thereby reducing the heat transfer from the boundary member or members to the fin and to the fluid flowing through the space.
The present invention provides a structure that is self-compensating so that regardless of variations of dimensions of the fin or fin strip, there is always provided a close and thereby effecient heat conducting relationship between the inner and outer tubes and the fin regardless of normal variations in dimensions from the design dimensions.